Residential air-to-water heat pumps (R290)

The power of a residential heat pump depends on three factors: the area of the house, the quality of insulation and the type of heating system. As a guideline, new construction with good insulation typically requires 60 to 80 W per square meter, a house with average insulation 80 to 120 W/m², and a poorly insulated older building can require up to 150 W/m². In practice, this means that a new house of 120 m² with good insulation can work with a 9 kW unit, while the same area in an older house with average insulation can require 12 kW or more. For larger houses above 200 m², 15 kW or 20 kW units come into consideration. Centro-Gas provides a professional sizing assessment before each installation, as no honest capacity recommendation can be given without knowing the specific house. That assessment is the correct first step, not guessing from a table.

Air-to-water heat pumps exist in two designs. A split system places the compressor outside and the hydraulic module inside, connected by pipes with refrigerant that must be joined on site by a technician with an F-gas certificate. A monoblock system contains all components of the refrigerant circuit in the outdoor unit and connects to the indoor heating circuit only with water pipes. The Centro-Gas range exclusively uses a monoblock design. The advantages are simpler installation (water pipes instead of refrigerant pipes), no need for an F-gas certificate when connecting, and the fact that the R290 charge remains sealed in the factory-tested outdoor unit. For homeowners, that means a faster installation day and one less possible point of failure. For technicians from related trades (plumbing, electrical), monoblock units are more accessible because on-site work includes water connections they already deal with.

The two most common refrigerants in residential heat pumps today are R290 (propane) and R32. The key difference is the impact on the environment, which is measured by the GWP value (global warming potential). R290 has a GWP of only 3, which means almost zero impact on the climate in case of leakage. R32 has a GWP of 675, and the older R410A (which is still found in many systems) has a GWP of 2,088. European F-gas regulations are gradually restricting refrigerants with high GWP, which makes R290 a choice with a greater future. Besides the ecological argument, R290 has a higher critical temperature (96.7 °C) than R32, which allows R290 heat pumps a water flow temperature of up to 75 °C. This is important in Serbia because many houses have older radiator systems designed for higher water temperatures. A heat pump that can reach 75 °C is more compatible with those existing systems without the need to replace radiators. The entire Centro-Gas residential range uses R290. The units carry an A+++ energy class at 35 °C flow temperature and remain highly efficient at 55 °C, which is the temperature at which most radiator retrofits actually work.

Yes, but compatibility depends on the type of radiator and the flow temperature your heating system requires. Modern low-temperature radiators (designed for flow water of 45 to 55 °C) work well with a heat pump and give high efficiency. Standard older radiators designed for 70 to 75 °C can also work, especially because Exinda R290 units can produce flow temperatures up to 75 °C, although efficiency at higher flow temperatures decreases compared to lower ones. Underfloor heating is an ideal pair because it works at low flow temperatures (30 to 40 °C), and that is precisely the range in which heat pumps achieve the highest SCOP values. Fan-coil units are also a good choice. In some houses, the best approach is a combination: underfloor heating on the ground floor with radiators on the upper floor, or oversized radiators that can work at lower flow temperatures. Centro-Gas assesses each house individually during a professional sizing assessment. If your radiators are too small for heat pump temperatures, the technician will tell you. An honest assessment before installation prevents problems after it.

A gas boiler converts approximately 0.9 kW of heat from each 1 kW of gas energy. A heat pump with an SCOP value of 4.0 delivers 4 kW of heat from 1 kW of electricity. This means that for each unit of energy invested, the heat pump produces approximately four times more heat. Actual savings on the bill depend on local electricity and gas prices, the heat load of the house, the quality of insulation, and the design of the heating system. Since electricity and gas prices in Serbia change and differ by distributor, stating a specific percentage of savings would be unreliable. What physics guarantees is that a properly sized and installed system consumes significantly less energy for the same heating effect compared to a gas boiler. State subsidies for energy-efficient heating can cover a significant part of the investment, which further shortens the payback period. Centro-Gas helps customers check current program conditions and prepare applications. The total cost of ownership over 10 to 15 years of operation, taking into account lower energy consumption, less maintenance, and help with subsidies, is the real framework for this comparison, not the price of the device itself.

Serbia has state and municipal subsidy programs that support the energy-efficient replacement of heating systems in residential buildings. These programs typically cover part of the equipment and installation costs. They are announced on an annual basis with deadlines for application, and the conditions can change between cycles. In addition to national programs of the Ministry of Mining and Energy, many municipalities in Serbia announce their own local calls for subsidies. International financing programs (such as EBRD green credit lines) are also available through participating banks. Centro-Gas monitors active programs and helps customers with the preparation of documentation as part of the installation service. Since subsidy conditions, eligibility criteria, and coverage amounts change with each program cycle, stating specific figures risks being outdated at the moment you read this. A practical approach is to contact Centro-Gas for current program details. Navigating through subsidies is a key part of the service, not an incidental thing. For a complete overview of subsidy programs, visit the [Centro-Gas subsidies page](/en/subsidies/).